The objectives of this project are to investigate the role of short repeated sequences (delta) in genome rearrangement in yeast. I have isolated numerous deletions and deletion-inversions at the locus of the ochre suppressor, SUP4. The uniform size of the deletions suggests that repeated sequence which surround this gene are promoting the deletion event. In addition, an adjacent segment also bounded by delta sequences has been observed to invert. These complex rearrangements are analogous to those observed in studies with bacterial transposition. I plan to DNA sequence the deletions and deletion-inversions to investigate the fate of the delta sequences. A method is described which facilitates the cloning of mutant sequences from a yeast strain. To further investigate the role of delta sequences in rearrangement, the SUP4 region from a yeast strain, known to have a different delta sequence arrangement near SUP4, will be screened for deletions. Additionally, unrelated yeast strains will be screened for sequence rearrangements near SUP4. The role of delta sequences (or nearby region if DNA sequencing reveals their importance) will be directly tested by specifically altering these regions in vitro by deletion, insertion and site-specific mutagenesis. The altered sequences will next be introduced back into yeast by transformation to study their effects on rearrangements at the SUP4 locus. I will also attempt to insert a delta sequence in vitro into new positions within the SUP4 region and test for novel rearrangements due to the inserted sequence. Finally, screening for mutations which affect deletion frequency at SUP4 will be undertaken to delineate what gene products are necessary for these rearrangement events.